Oblique tip endoscope with zero degree field angle

ABSTRACT

Systems, apparatuses, and methods are discussed herein for an endoscope. The endoscope has a distal tip with an oblique portion and a flat portion, the oblique portion defines a plane that forms an angle between and including 20 and 40 degrees to a central axis of the endoscope. A related sheath may have similar features at the distal tip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional application Ser. No.62/121,814 filed Feb. 27, 2015, and titled, “Oblique tip endoscope withzero degree field angle,” which provisional application is incorporatedby reference herein in its entirety as if reproduced in full below.

BACKGROUND

Medical endoscopes are inserted into the patient either through anorifice, incision, or other entry point. In many applications, thecritical dimension of the orifice is smaller than the diameter of theendoscope cross-section, which means the orifice expands to accommodatethe endoscope. Depending on the tissue structure, mechanical properties,and proximity to nerves, the deformation caused by insertion of theendoscope may result in tissue trauma and pain.

To reduce pain, many times the diameter of the endoscope is reduced;however, the diameter must be large enough to contain the functionalcomponents of the endoscope, and as such the diameter is oftenpractically limited.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various embodiments, reference will now bemade to the accompanying drawings in which:

FIG. 1 shows a side elevation view of an endoscope in accordance withcertain embodiments of the present disclosure.

FIG. 2 shows a schematic side elevation view of the distal end of theendoscope of FIG. 1 in accordance with certain embodiments of thepresent disclosure.

FIG. 3A shows a magnified partial-perspective view of the distal end ofan endoscope in accordance with certain embodiments of the presentdisclosure.

FIG. 3B shows and left and right side elevation views, and FIG. 3C showsan overhead view, of a distal tip of an endoscope in accordance withcertain embodiments of the present disclosure.

FIG. 4 shows an end elevation view of an endoscope in accordance withcertain embodiments of the present disclosure.

FIGS. 5A and 5B show side elevation views of a sheath for an endoscopein accordance with certain embodiments of the present disclosure.

FIG. 6A shows a magnified partial-perspective view of a distal end of asheath in accordance with certain embodiments of the present disclosure.

FIG. 6B shows a side elevation view, and 6C shows an overhead view, of adistal tip of a sheath in accordance with certain embodiments of thepresent disclosure.

FIG. 7A shows a perspective view of an endoscope telescoped in a sheathin accordance with certain embodiments of the present disclosure.

FIG. 7B shows an exploded perspective view of a sheath and an endoscopebefore the endoscope is telescoped in the sheath in accordance withcertain embodiments of the present disclosure.

FIG. 8 shows a magnified partial-perspective view of an endoscopetelescoped in a sheath in accordance with certain embodiments of thepresent disclosure.

FIG. 9 is a flowchart of a method of using endoscopes and combinationdevices in accordance with certain embodiments of the presentdisclosure.

FIG. 10 is a flowchart of a method of fabrication of an endoscope inaccordance with certain embodiments of the present disclosure.

FIG. 11 shows a plot of insertion force as a function of angle of anoblique feature.

SUMMARY

An example embodiment is an endoscope comprising: an elongated shaftthat defines a central axis, a proximal end, and a distal tip, theelongated shaft defines a cross-section along a portion of the elongatedshaft; a first portion of the distal tip, wherein the first portiondefines a first plane that forms an angle of between and including 20and 40 angular degrees to the central axis; and a second portion of thedistal tip, wherein the second portion defines a second plane that isperpendicular to the central axis. The example endoscope furthercomprises: a first transition area on a first side of the distal tipbetween the first portion and the second portion, the first transitionarea smoothly varying between the first portion and the second portion;a second transition area on a second side of the distal tip opposite thefirst side, the second transition area smoothly varying between thefirst portion and the second portion; and a view port coupled to theproximal end of the elongated shaft, the view port extends away from thecentral axis. The example endoscope further comprise: a first channelwithin the elongated shaft that terminates at the first portion; asecond channel within the elongated shaft that terminates at the secondportion, the second channel fluidly isolated from the first channelalong a length of the elongated shaft; and a visualization conduit thatextends through the view port and the second channel, the visualizationconduit optically exposed at the second plane such that a viewing anglethrough the visualization conduit is parallel to the central axis.

Other example embodiments are an endoscope and sheath system. Theexample endoscope comprises: an endoscope elongated shaft that definesan endoscope central axis, an endoscope proximal end, and an endoscopedistal tip, the endoscope elongated shaft defines a cross-section alonga portion of the endoscope elongated shaft; an endoscope first portionof the endoscope distal tip defines a first plane that forms an angle ofbetween and including 20 and 40 angular degrees to the endoscope centralaxis; an endoscope second portion of the endoscope distal tip defines asecond plane that is perpendicular to the endoscope central axis; and anendoscope first transition area on a first side of the endoscope distaltip between the endoscope first portion and the endoscope secondportion, the endoscope first transition area smoothly varying betweenthe endoscope first portion and the endoscope second portion. Theexample endoscope further comprises: an endoscope second transition areaon a second side of the endoscope distal tip opposite the first side,the endoscope second transition area smoothly varying between theendoscope first portion and the endoscope second portion; a view portcouple to the proximal end of the endoscope elongated shaft, the viewport extends away from the endoscope central axis; a first channelwithin the endoscope elongated shaft that terminates at the endoscopefirst portion; a second channel within the endoscope elongated shaftthat terminates at the endoscope second portion, the second channelfluidly isolated from the first channel along a length of the endoscopeelongated shaft; and a visualization conduit that extends through theview port and the second channel, the visualization conduit opticallyexposed at the second plane such that a viewing angle through thevisualization conduit is parallel to the endoscope central axis. Theexample system further includes a sheath comprising: a sheath elongatedshaft that defines a sheath central axis, a sheath proximal end, and asheath distal tip, the sheath elongated shaft defines a circularcross-section along a portion of the sheath elongated shaft; a sheathfirst portion of the sheath distal tip defines a third plane parallel tothe first plane; a sheath second portion of the sheath distal tipdefines a fourth plane parallel to the second plane; and a sheath firsttransition area on a first side of the sheath distal tip between thesheath first portion and the sheath second portion, the sheath firsttransition area smoothly varying between the sheath first portion andthe sheath second portion. The example sheath further comprises: asheath second transition area on a second side of the sheath distal tipopposite the first side, the sheath second transition area smoothlyvarying between sheath first portion and the sheath second portion; aplurality of apertures disposed a sheath distal end of the sheathelongated shaft proximate to the sheath first portion; and an insertionport at the sheath proximal end of the sheath elongated shaft, theendoscope elongated shaft telescoped through the sheath insertion port.

Example methods comprise: positioning a distal tip of an endoscope toabut an aperture into a patient's body, a distal tip of the endoscopehaving a first feature that defines a first plane that forms an anglewith a central axis of the endoscope, and a second feature that definesa second plane perpendicular to the central axis of the endoscope;inserting the distal tip of the endoscope through the aperture into thepatient's body, wherein insertion force of the distal tip into theaperture is less than 80% of an insertion force of an endoscope with ablunt front and having a same outer dimension of an elongated shaft asthe endoscope having the first and second features; and visualizing aninterior portion of the patient's body at a viewing angle that isparallel to the central axis.

Other example methods comprise: positioning a distal tip of an endoscopeto abut an aperture into a patient's body, a distal tip of the endoscopehaving a first portion that defines a first plane that forms an anglebetween and including 20 and 40 angular degrees with a central axis ofthe endoscope, and a second feature that defines a second planeperpendicular to the central axis of the endoscope; inserting the distaltip of the endoscope through the aperture into the patient's body; andvisualizing an interior portion of the patient's body at a viewing anglethat is parallel to the central axis.

Yet still other example methods comprise assembling an endoscope by:obtaining an outer tube that comprises: a first central axis, a firstproximal end, and a first distal tip; a first portion at the firstdistal tip defines a first plane that forms an angle of between andincluding 20 and 40 angular degrees to the first central axis; and asecond portion at the first distal tip that defines a second planeperpendicular to the first central axis; obtaining an inner tube thatcomprises: a second central axis, a second proximal end, and a seconddistal tip; a first portion at the second distal tip defines a thirdplane that forms an angle of between and including 20 and 40 degrees tothe second central axis; and a second portion at the second distal tipthat defines a fourth plane perpendicular to the second central axis;telescoping the inner tube into the outer tube until the first and thirdplanes are coplanar and two channels are defined within the outer tube,the first channel within the inner tube, and the second channel definedbetween the inner tube and an inside surface of the outer tube;telescoping within the second channel a visualization conduit; couplingthe visualization conduit to an eyepiece in viewing port; and opticallyexposing the visualization conduit at the first distal end with viewingangle parallel to the first central axis.

Definitions

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, different companies may refer to a component by differentnames. This document does not intend to distinguish between componentsthat differ in name but not function. In the following discussion and inthe claims, the terms “including” and “comprising” are used in anopen-ended fashion, and thus should be interpreted to mean “including,but not limited to . . . .” Also, the term “couple” or “couples” isintended to mean either an indirect or direct connection. Thus, if afirst device couples to a second device, that connection may be througha direct connection or through an indirect connection via other devicesand connections.

An “elliptical cross-section” shall mean a closed curve on a planesurrounding two focal points such that the sum of the distances to thetwo focal points is constant for every point on the curve. A circularcross-section is a special case of the elliptical cross-section wherethe two focal points are collocated.

A “visualization conduit” shall mean a medium through whichvisualization takes place during use of an endoscope. The visualizationconduit may be, for example, a rod lens or an optical fiber bundle. Thefact that the visualization conduit can carry illumination to theviewing area shall not obviate the status as a visualization conduit.

A “light fiber bundle” shall mean a plurality of optical fibers throughwhich light is carried to illuminate an area of visualization (thevisualization through a separate visualization conduit). The fact thateach optical fiber can theoretically be used to provide visualization,albeit of low resolution, shall not obviate the status a light fiberbundle (individually or as a group) as a light fiber bundle.

A “combination device,” shall mean the device created when an endoscopeis telescoped (disposed) in a sheath, in order to differentiate thecombination device from the un-sheathed endoscope devices discussedherein. In practice, it is appreciated that the combination device maybe referred to as an “endoscope” or an “endoscope device.”

An “insertion force” shall mean the force to insert a distal tip of anendoscope through a one inch diameter, 0.125 inch thickness medicalgrade rubber membrane with a pre-punched 1 millimeter (mm) diameterhole.

“Blunt front” shall mean an endoscope or sheath whose distal tip hasonly a single feature, and that single feature forms a planeperpendicular to a central axis of the endoscope or sheath.

“Coplanar,” with respect to features of endoscopes, sheaths, orcomponents that are assembled to construct an endoscope, shall alsoinclude parallel planes defined by the respective features where theperpendicular distance between the planes is 0.5 millimeters or less.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments. Althoughone or more of these embodiments may be preferred, the embodimentsdisclosed should not be interpreted, or otherwise used, as limiting thescope of the disclosure, including the claims. In addition, one skilledin the art will understand that the following description has broadapplication, and the discussion of any embodiment is meant only to beexemplary of that embodiment, and not intended to intimate that thescope of the disclosure, including the claims, is limited to thatembodiment.

The apparatuses, systems, and methods discussed herein relate to anendoscope comprising an oblique or angled feature on the distal end(hereafter oblique portion), a sheath comprising an oblique or angledfeature on the distal end (hereafter oblique portion), and a combinationof the endoscope and sheath where the endoscope is telescoped (disposed)in the sheath to form a combination device. The various example systemsare also directed to endoscopes and related devices with features thatreduce insertion force, and therefore reduce trauma, pain, and recoverytime for the patient. More particularly, the embodiments discussedherein have an oblique portion on the distal end that results in agradual dilation of the orifice during insertion, which reduces trauma.However, to ensure proper visualization for endoscopes, the distal endof the endoscope also comprises a feature that defines a planeperpendicular to the long axis of the endoscope (hereafter flat portion)such that the view of a visualization conduit is along the long axis ofthe endoscope. That is, the viewing angle is approximately a zero degreefield angle. The oblique portion at the distal tip eases insertion ofthe scope through an aperture in a patient's body and therefore reducesthe force employed for insertion.

The figures discussed below illustrate various embodiments ofendoscopes, sheaths, and combination devices. The various featurescomprising and defining these devices are discussed on multiple figuresin different perspective views and scales, each feature is identified inthe first instance of its appearance in a figure and may be furtherreferenced in other figures but not explicitly identified due to theperspective of the other figure or figures.

FIG. 1 shows a side elevation view of an endoscope 100 in accordancewith example embodiments of the present disclosure. In particular, FIG.1 shows endoscope 100 comprising a central axis 107, a proximal end 120,a distal end defined by a distal tip 112, an inflow port 102, and anoptics port 104 through which light is provided to a light fiber bundle(not visible in FIG. 1). In the example embodiment, the inflow port 102and the optics port 104 may each extend perpendicularly from the centralaxis 107 of the endoscope 100, but other relationships are contemplated.The endoscope 100 may also comprise a viewing port 106 that may form anangle α of about 40 angular degrees as measured from the central axis107 of the endoscope 100. The viewing port 106 has disposed therein avisualization conduit that extends from the viewing port 106 to thedistal tip 112. The visualization conduit is not visible in the view ofFIG. 1, but is discussed in greater detail below. The endoscope furthercomprises an elongated shaft 108 having a length 116 from a proximal end110 of the elongated shaft 108 to the end 112A of the distal tip 112. Inthe example embodiment, the length 116 is about 226.4 millimeters (mm),but longer and shorter lengths are also contemplated. The elongatedshaft 108 defines within an interior volume a first channel (not visiblein FIG. 1) that extends along the central axis 107 of the endoscope 100.The elongated shaft 108 is coupled to an insertion valve 114, and in usevarious tools (e.g., shavers, ablation devices) may be telescoped intothe first channel of the elongated shaft 108 through the insertion valve114.

FIG. 2 shows a cross-sectional elevation view of the distal tip 112 ofthe endoscope 100. In particular, the distal tip 112 comprises a featurein the form of an angled or oblique portion 216 that defines a plane. Inthe view of FIG. 2 the plane defined by the oblique portion 216 isperpendicular the page, and thus the plane is visible only as line 202.The plane defined by the oblique portion 216 (visible as line 202) formsan angle β with the central axis 107 of the endoscope, which angle 1 maybe between about 20 and 40 angular degrees in some cases, in other casesmay be between about 30 and 34 angular degrees, and in yet still othercases may be about 32 angular degrees. The distal tip 112 also comprisesa flat portion 228 that defines a second plane. In the view of FIG. 2the second plane defined by the flat portion 228 is perpendicular thepage, and thus the plane defined by the flat portion 228 is visible onlyas line 208. The plane defined by the flat portion 228 (visible as line208) is perpendicular to the central axis 107 of the elongated shaft108. In an example embodiment, the length 214 may be about 5.5 mm, butselection of the angle 1 affects the length 214. The distal tip 112further comprises a length 214 measured from a proximal portion 250 ofthe oblique feature 216 to the flat portion 228. The distal tip 112 alsodefines a height 236 measured perpendicular to the central axis 107, anda width (delineated with respect to FIG. 3C, discussed more below). Theendoscope 100 may also define two interior channels, the first indicatedby 230 and the second indicated by 206.

FIG. 3A shows elevation views of the distal end of the endoscope 100.FIG. 3B shows left and right side elevation views of the distal tip 112of the endoscope 100. FIG. 3C shows a top elevation view of the distaltip 112. FIGS. 3A-3C are discussed interchangeably herein. The exampleendoscope comprises first channel 230 that runs parallel to the centralaxis 107. During use of the endoscope the first channel 230 may beemployed for fluid flow and/or instrumentation. The first channel 230 atthe distal tip 112 defines an upper smoothly curved surface 318, and aflat surface (straight portion) 314 opposite an apex of the curvedsurface 318. The distal tip 112 is defined, at least in part, by theoblique portion 216 and the flat portion 228. Between the obliqueportion 216 and the flat portion 228 resides a first transition area 306on a first side 320 of the distal tip 112. In example embodiments, thefirst transition area 306 smoothly varies between the oblique portion216 and the flat portion 228. The distal tip 112 further comprises asecond transition area 308 on a second side 322 of the distal tip 112,the second transition area 308 opposite first transition area 306. Thesecond transition area 308 smoothly varies between the oblique portion216 and the flat portion 228. In example embodiments, each transitionarea 306 and 308 defines a radius of curvature (i.e., radius ofcurvature 307 for transition area 306, and radius of curvature 309 fortransition area 308 (FIG. 3B)). The radius of curvature for eachtransition area is discussed more below after introduction of thevarious outside dimensions of the elongated shaft 108 (in reference toFIG. 4). The upper smoothly curved surface 318 may also be referred toas a transition area.

Still referring to FIGS. 3A-3C, the second channel is defined by asmoothly curved surface 312 of the endoscope 100 and by the flat surface314 of the first channel 230. In the example system shown, avisualization conduit 304 is disposed in the second channel parallel tothe central axis 107. The visualization conduit 304 terminates in such away that the viewing angle is parallel to the long central axis 107(i.e., there is about a zero degree field viewing angle). For example,the visualization conduit 304 may terminate at or along (flush or nearlyflush with) the plane defined by the flat portion 228 (visible as line208 (FIGS. 2 and 3B)). Also disposed in the second channel are aplurality of optical fibers that make up the light fiber bundle 316.

FIG. 4 shows an end elevation view of the distal tip 112 of theendoscope 100 in FIG. 1. In particular, FIG. 4 shows a largest outerdimension 402 of the elongated shaft 108 measured perpendicularly to thecentral axis 107. A further outside dimension 416 is also shown, whichis measured perpendicular to the largest outside dimension 402 and whichmay be equal to or smaller than the largest outside dimension 402. FIG.4 further shows the visualization conduit 304 disposed equidistant inbetween a first side 408 and a second side 410 of the flat surface 314of the second channel 206, but in other example cases the visualizationconduit may be disposed favoring one side or another. Also shown are twoaxes 412 and 414, each of which pass through the central axis 107 andare perpendicular to the central axis 107 and to each other.

Referring simultaneously to FIGS. 1, 2, 3A-3C, and 4, which each showdifferent views of the endoscope 100, the example endoscope 100comprises elongated shaft 108 that defines a central axis 107, aproximal end 120, and a distal tip 112. The distal tip 112 includes anoblique portion 216 that defines a plane (shown as line 202) that formsan angle with respect to the central axis 107. The distal tip 112 alsoincludes a flat portion 228 that defines a plane (shown as line 208)that is perpendicular to the central axis 107. The first transition area306 is disposed on the first side 320 of the distal tip 112 between theoblique portion 216 and the flat portion 228, and the first transitionarea 306 smoothly varies between the oblique portion 216 and the flatportion 228. The example endoscope comprises the second transition area308 on the second side 322 of the distal tip 112 opposite the first side320, and the second transition area 308 smoothly varies between theoblique portion 216 and the flat portion 228. In an example embodiment,the viewing port 106 is coupled to the proximal end 110 of the elongatedshaft 108 and the viewing port 106 extends away from the central axis107. The first channel 230 within the elongated shaft 108 terminates atleast in part at the oblique portion 216. The second channel 206 withinthe elongated shaft 108 terminates at the flat portion 228, and thesecond channel 206 is fluidly isolated from the first channel 230 alonga length 116 of the elongated shaft 108.

In the example endoscope, the visualization conduit 304 extends throughthe viewing port 106 and the second channel 206, and is opticallyexposed at the second plane (shown as line 208) such that a viewingangle through the visualization conduit 304 is parallel to the centralaxis 107. In example embodiments, the elongated shaft 108 defines anoval or elliptical cross-section over at least a portion of theelongated shaft 108, and in some cases along the entire elongated shaft108. As defined above, elliptical cross-section includes, as a specialcase, circular cross-sections, and thus in some cases the elongatedshaft 108 may be circular over all or part of its length. The endoscope100 may further comprise the plurality of optical fibers that make up alight fiber bundle 316 disposed within the second channel 206 along withthe visualization conduit 304. The light fiber bundle 316 may beoptically exposed at the second plane (shown as line 208), and likewisethe light fiber bundle 316 is optically connected to the optics port104. The elongated shaft 108 defines a largest outside dimension 402measured perpendicularly to the central axis 107 (e.g., measured alongaxis 412), and the elongated shaft 108 defines a further outsidedimension 416 also measured perpendicularly to the central axis 107(e.g., measured along axis 414). The further outside dimension 416 maybe equal to or smaller than the largest outside dimension 402.

Again, the example distal tip 112 comprises a plurality of transitionareas, including a first transition area 306 that defines a first radiusof curvature 307 between and including 8% and 20% of the largest outsidedimension 402, and a second transition area 308 defines a second radiusof curvature 309 between and including 8% and 20% of the largest outsidedimension 402. In the example embodiment, the endoscope 100 furthercomprises a upper smoothly curved surface 318 on the oblique portion 216between the first 306 and second 308 transition areas, the uppersmoothly curved surface 318 smoothly varies from the plane defined bythe oblique portion 216 to an outside diameter of the elongated shaft108.

The example first channel 230 may comprise a “D” cross-sectional shapeas shown in FIG. 4. The cross-sectional shape shown in FIG. 4 defines aflat surface 314 parallel to the further outside dimension 416, and acurved portion 418 coupled on each side 408, 410, to the flat surface314. The first channel 230 has a height 420 measured from an apex 422 ofthe curved portion 418 to the flat surface 314. In some embodiments, thefirst channel 230 height 420 is greater than half of the largest outsidedimension 402 of the elongated shaft 108, but smaller than an internaldimension 234 (FIG. 2) of the elongated shaft 108, as measured parallelto the largest outside dimension 402.

The example endoscope 100 discussed above may be employed using themethods discussed below alone or in combination with a sheath, and anexample sheath is discussed below in FIGS. 5A-5C and 6A-6C.

FIG. 5A shows a side elevation view of a sheath 500 in accordance withcertain embodiments of the present disclosure. In particular, the sheath500 defines a proximal end 502 and a distal end 504, and the distal end504 comprises a distal tip 506 (discussed in greater detail with respectto FIGS. 6A-6C). The sheath 500 comprises elongated shaft 508 thatdefines an interior channel (not visible in FIG. 5A, but discussed morebelow). In some embodiments, the interior channel, through which variousinstruments may be inserted for surgical procedures (e.g., the endoscope100), may also be used for fluid flow. The interior channel may extendfrom a connector portion 512 on the proximal end 502 of the sheath 500to the distal end 504. The connector portion 512 may be configured invarious manners to couple to and/or enable telescoping of an endoscope.

The example sheath 500 comprises a fluid port 510 located in proximityto the proximal end 502. The fluid port 510, when the valve of the portis open, is in fluid communication with the interior channel defined bythe elongated shaft 508, and thus fluid may flow into or out of theinterior channel by way of the fluid port 510. The distal tip 506 may bedefined by a plurality of features including an oblique portion 516 anda flat portion 518. The oblique portion 516 defines a plane. In the viewof FIG. 5A the plane defined by the oblique portion 516 is perpendicularthe page, and thus the plane is visible only as line 514. The planedefined by the oblique portion 516 (visible as line 514) forms an angleγ with the central axis 107 of the sheath 500, which angle γ may bebetween about 30 and 34 angular degrees, and in some embodiments may beabout 32 angular degrees.

FIG. 5B shows a side elevation view of the example sheath 500. Referringsimultaneously to FIGS. 5A and 5B, the flat portion 518 also defines aplane. In the view of FIG. 5B, the plane defined by the flat portion 518is perpendicular the page, and thus the plane is visible only as line520. The plane defined by the flat portion 518 (visible as line 520) isperpendicular to the central axis 107 of the elongated shaft 508. Inexample embodiments, the elongated shaft 508 may comprise a plurality ofapertures 532 disposed circumferentially around at least a portion ofthe circumference of the shaft and along a predetermined length of theelongated shaft 508, where the predetermined length may be less than anoverall length (shown and discussed in FIG. 5B). The plurality ofapertures 532 may comprise various shapes, sizes, and locations,including uniform and non-uniform arrays.

Referring specifically to FIG. 5B, example sheath 500 comprises anoverall length 522 extending from the distal tip 506 to the proximal end502, and a shaft length 524. The shaft length 524 may be defined asextending from the distal end 526 of the connector portion 512 to thedistal tip 506. The connector portion 512 comprises a length 530measured from the distal end 526 of the connector 512 to the proximalend 502 along the central axis 107. In example embodiments, the sheath500 may have a length 522 of about 225.6 mm, a shaft length 524 of about204.2 mm, and a connector portion 512 length 530 of about 25 mm. Longerand short lengths are also contemplated.

FIG. 6A shows a magnified partial-perspective view of the distal tip 506of the sheath 500. FIG. 6B shows left and right elevation views of thedistal tip 506 of the sheath 500. FIG. 6C shows an overhead view of thedistal tip 506 of the sheath 500. FIGS. 6A-6C are discussed interinterchangeably herein. In an example embodiment, the distal tip 506comprises the oblique portion 516 and flat portion 518. Oblique portion516 defines a plane, and in the view of FIG. 6B the plane defined by theoblique portion 516 is visible as a line 514. Flat portion 518 likewisedefines a plane, and in the view of FIG. 6B the plane defined by theflat portion 518 is visible as a line 520. The distal tip 506 furthercomprises a first transition area 602 on a first side 604 of the distaltip 506 between the oblique portion 516 and the flat portion 518. Thefirst transition area 602 smoothly varies between the oblique portion516 and the flat portion 518. The second transition area 606 is locatedon a second side 608 opposite the first side 604, and the secondtransition area 606 smoothly varies between the oblique portion 516 andthe flat portion 518.

Referring simultaneously to FIGS. 5A-5B and 6A-6C, the example sheath500 comprises elongated shaft 508 that defines a central axis 107, aproximal end 502, and a distal tip 506. The elongated shaft 508 definesa largest outside dimension 612 along a portion of the elongated shaft508. The oblique portion 516 of the distal tip 506 defines a plane(visible as line 514 in FIG. 66) that forms an angle γ, the angle γbeing between and including about 20 and about 40 angular degrees to thecentral axis 107. In some cases, the angle γ may be between andincluding about 30 to about 34 angular degrees, and in other cases theangle may be about 32 angular degrees. The first transition area 602resides on the first side 604 of the distal tip 506 between the obliqueportion 516 and the flat portion 518, with the first transition area 602smoothly varying between the oblique portion 516 and the flat portion518. The second transition area 606 resides on the second side 608 ofthe distal tip 506 opposite the first side 604, the transition area 606smoothly varying between oblique portion 516 and the flat portion 518.The first transition area 602 defines a radius of curvature 622 betweenand including 8% and 20% of the largest outside dimension 612, and thetransition area 606 likewise defines a radius of curvature 624 betweenand including 8% and 20% of the largest outside dimension 612. In anembodiment, an inner dimension 618 of the sheath 500 may be about 5.3mm. The example distal tip 506 may also comprise a third transition area610 on the oblique portion 516 between the first 602 and secondtransition 606 areas, the third transition area 610 smoothly varyingfrom the plane defined by the oblique portion 516 (visible as line 514in FIG. 6B) to a largest outside dimension 612 of the elongated shaft108. In example sheaths where the cross-sectional shape of the sheath iselliptical (and the focal points are not collocated), a second (further)outside dimension 614, measured perpendicular to the largest outsidedimension 612, may be equal to or less than the largest outsidedimension 612.

In example sheaths, an insertion port 528 may be part of the connectorportion 512 at the proximal end 502 of the elongated shaft 108, and theinsertion port 528 may be configured to couple to a proximal end of anendoscope (e.g., endoscope 100) when the endoscope is telescoped throughthe insertion port 528.

FIG. 7A shows a perspective view of an endoscope telescoped in a sheath.In particular, in the combination device 700A the example endoscope 100is telescoped in an example sheath 500. FIG. 7B shows an exploded viewof each device 100, 500, separately with the central axis 107 alongwhich both devices are aligned. When telescoped (as in the embodiment asshown in FIG. 7A) the planes formed by the oblique portions of eachdevice (the planes visible as lines 514 and 202 in FIG. 7B) areparallel, and in some cases coplanar. When telescoped, the planes formedby the flat portions of each device (the planes visible as lines 208 and520) are parallel. As discussed at least in the method 1000 in FIG. 10,the endoscope 100 may be telescoped in the sheath 500 and may beremovably mechanically coupled to one another.

FIG. 8 shows a magnified perspective view of the distal end of anexample combination device 700A. In particular, FIG. 8 shows an examplealignment of oblique portion 216 of the endoscope 100 and obliqueportion 516 of the sheath 500. In particular, in the view of FIG. 8 theplane defined by the oblique portion 216 of the endoscope (the plane notspecifically shown) and the planed formed by the oblique portion 516 ofthe sheath (the plane not specifically shown) are parallel. The parallelnature of the planes may be a design characteristic of the devices, ormay stem from variations in length attributable to manufacturingtolerances. That is, though shown in large scale in FIG. 8, the distaltips of the devices are on the order of 5 mm in largest outsidedimension. Having the planes defined by the oblique portions 216/516 beexactly coplanar be difficult in the defined scale, and thus as definedabove coplanar includes the situation where planes defined by theoblique portions 216/516 are parallel and where the perpendiculardistance between the planes is 0.5 millimeters or less. In addition tothe alignment of the oblique portions 216 and 516, when telescoped theflat portions 518 and 228 are parallel as shown.

The devices discussed above may be manufactured and used alone and incombination according to various methods including but not limited tothe methods discussed below in FIGS. 9 and 10.

FIG. 9 shows a method 900 of use of an endoscope device. The examplemethod 900 comprises positioning, at block 902, a distal tip of anendoscope to abut an aperture into a patient's body. The distal tip ofthe endoscope comprises an oblique portion which defines a plane thatforms an angle with a central axis of the endoscope as discussed above.The distal tip of the endoscope may also comprise a flat portion whichdefines a second plane perpendicular to the central axis of theendoscope. At block 904, the distal tip of the endoscope is insertedthrough the aperture into the patient's body, using insertion force ofless than 80% of an insertion force of an endoscope with a blunt fronthaving the same outer dimension(s) (402, 416 in FIG. 2) as theendoscope. At block 906, an interior portion of the patient's bodyaccessed through the aperture is visualized (e.g., by using avisualization conduit) at a viewing angle that is parallel to thecentral axis and may be referred to as a zero-degree angle. In someembodiments, inserting the distal tip at block 904 further comprisesinserting the distal tip using the insertion force of less than 75% ofan insertion force of an endoscope with a blunt front having the sameouter dimension(s) (402, 416 in FIG. 2) as the endoscope. As discussedherein, an endoscope with a blunt front having the same outer dimensionsis one that comprises an outer dimension the same as elongated shafts108 and 508 discussed herein, and does not refer to a dimension of theoblique or flat portion of the distal tip 112/506.

In an example embodiment, positioning the distal tip at block 902further comprises positioning the distal tip with the endoscopetelescoped within a sheath. In this embodiment, the sheath comprises afirst feature that defines a plane at least parallel (and possiblycoplanar as defined) to the plane defined by the oblique portion of theendoscope, and the sheath has a second feature that defines a planeparallel to the plane defined by the flat portion of the endoscope. Inthe example embodiment, inserting the distal tip at block 904 furthercomprises simultaneously inserting both the sheath and the endoscopeusing an insertion force being less than 80% of an insertion force of asheath and the endoscope with blunt fronts. In alternate embodiments,inserting the sheath and endoscope further comprises using an insertionforce of less than 75% of an insertion force of a sheath and endoscopewith blunt fronts. The combination device may employed in a variety ofsurgical procedures, including embodiments where positioning at block902 further comprises positioning at a structure along a female genitaltract of a patient, and in an alternate embodiment, positioning at block902 further comprises positioning at the cervix of the patient.

In an alternate embodiment, at block 902, the distal tip of an endoscopeis positioned to abut an aperture into a patient's body and comprisesthe oblique portion that defines a plane that forms an angle between andincluding 20 and 40 degrees with a central axis of the endoscope, and aflat portion that defines a plane perpendicular to the central axis ofthe endoscope. At block 904, the distal tip of the endoscope may beinserted through the aperture into the patient's body, and at block 906,an interior portion of the patient's body may be visualized at a viewingangle that is parallel to the central axis. In another exampleembodiment, inserting the distal tip at block 902 further comprisesinserting with the oblique portion of the endoscope forming an angle ofbetween and including 30 and 34 angular degrees, and in yet anotheralternate embodiment, inserting the distal tip further comprisesinserting with the oblique portion of the endoscope forming an angle ofabout 32 angular degrees.

In some embodiments, positioning the distal tip at block 902 furthercomprises positioning the distal tip with the endoscope telescopedwithin a sheath along the central axis shared by the sheath and theendoscope. In this embodiment, the sheath comprises an oblique portionthat defines a plane parallel (and in some cases coplanar s defined)with the plane defined by the oblique feature of the endoscope, and thesheath has a flat portion that defines a plane parallel with the planedefined by the blunt portion of the endoscope. In some embodiments,inserting the distal tip at block 904 further comprises simultaneouslyinserting both the sheath and the endoscope. In an embodiment,positioning at block 902 further comprises positioning at a structurealong a female genital tract of a patient, and in an alternateembodiment positioning at block 902 further comprises positioning at thecervix of the patient.

FIG. 10 shows a method 1000 of fabricating an endoscope, such as exampleendoscope 100. The example method 1000 comprises assembling an endoscopeby obtaining an outer tube at block 1002. The outer tube may comprise afirst central axis, a first proximal end, and a first distal tip. Anoblique portion at the first distal tip defines a plane that forms anangle of between and including 20 and 40 angular degrees to the firstcentral axis, and a flat portion at the first distal tip that defines aplane perpendicular to the first central axis. In some embodiments,obtaining the outer tube at block 1002 further comprises obtaining anouter tube where the plane defined by the oblique portion forms an anglewith the first central axis between and including 30 and 34 angulardegrees, and in other embodiments obtaining the outer tube furthercomprises obtaining an outer tube where the plane defined by the obliqueportion forms an angle of about 32 angular degrees.

The example method, at block 1004 further comprises obtaining an innertube that comprises a second central axis, a second proximal end, and asecond distal tip. In the example embodiment, an oblique portion at thesecond distal tip defines a plane that forms an angle of between andincluding 20 and 40 angular degrees to the second central axis, and aflat portion at the second distal tip that defines a plane perpendicularto the second central axis. In the example embodiment at block 1006, themethod comprises telescoping the inner tube into the outer tube untilthe plane defined by the oblique portion of the outer tube is coplanarwith the plane defined by the oblique feature of the inner tube.Moreover, telescoping the inner tube into the outer tube forms twochannels within the outer tube, the first channel within the inner tube,and the second channel defined between the inner tube and an insidesurface of the outer tube. In some embodiments, subsequent totelescoping the inner tube into the outer tube at block 1006, the methodcomprises soldering, at block 1008, the inner tube to the outer tube atthe first distal and second distal tips and soldering the inner tube tothe outer tube at the first and second proximal ends. At block 1010, avisualization conduit may be telescoped within the second channel and,at block 1012, the visualization conduit may be coupled to an eyepiece(e.g., a viewing port, such as 106 in FIG. 1). At block 1014, a lightfiber bundle may be telescoped in the second channel with thevisualization conduit and optically exposed at the plane defined by theblunt portion of the outer tube.

In some embodiments, obtaining the outer tube at block 1002 furthercomprises obtaining the outer tube that comprises: a first dimensionmeasured perpendicularly to the first central axis, and the outer tubedefines a second dimension measured perpendicularly to the first centralaxis and at a right angle to the first dimension, the second dimensionequal to or smaller than the first dimension; a first transition area ona first side of the first distal tip between the first portion and thesecond portion of the outer tube, the first transition area smoothlyvarying between the first portion and the flat portion of the outertube; a second transition area on a second side of the first distal tipopposite the first side, the second transition area smoothly varyingbetween the first portion and the flat portion of the outer tube. Inalternate embodiments, obtaining the outer tube at block 1002 furthercomprises obtaining the outer tube comprising the first transition areathat defines a radius of curvature between and including 8% and 20% ofthe first dimension and comprising the second transition area thatdefines a radius of curvature between and including 8% and 20% of thefirst dimension.

In further example embodiments, obtaining the inner tube at block 1004further comprises obtaining the inner tube that comprises: a thirddimension measured perpendicularly to the second central axis, and theinner tube defines a fourth dimension measured perpendicularly to thesecond central axis and at a right angle to the third dimension, thefourth dimension equal to or smaller than the third dimension; a thirdtransition area on a third side of the second distal tip between thefirst portion and the blunt portion of the inner tube, the thirdtransition area smoothly varying between the first portion and the bluntportion of the inner tube; a fourth transition area on a second side ofthe second distal tip opposite the first side, the second transitionarea smoothly varying between the first portion and the blunt portion ofthe inner tube. In some embodiments, obtaining the inner tube at block1004 comprises obtaining the inner tube comprising the third transitionarea defining a radius of curvature between and including 8% and 20% ofthe third dimension and comprising the fourth transition area thatdefines a radius of curvature between and including 8% and 20% of thefourth dimension.

In alternate embodiments, obtaining the inner tube at block 1004 furthercomprises obtaining the inner tube that comprises a cross-sectionalshape perpendicular to the second central axis. The cross-sectionalshape defines a straight portion and a curved portion coupled on eachend to the straight portion, as well as a first height measured from anapex of the curved portion to the straight portion. In an embodiment,the first height is greater half the first dimension of the outer tube,but smaller than an internal dimension of the outer tube measuredparallel to the first dimension. In various embodiments, at least one ofthe inner tube or an outer tube comprises a metallic material such asstainless steel, titanium, cobalt chrome, or combinations thereof.

EXAMPLES

Below are non-limiting examples of embodiments of endoscopes discussedherein. In order to establish that the angle of the oblique portion onthe distal end of a device reduces insertion force (and thereforereduces trauma and/or pain) as compared to blunt front device, testswere performed to measure insertion forces for a series of differentangles for the angle feature. In an embodiment, the testing discussedbelow employed a Mark-10 Series 5, 50 lb-f, 8000FZ, 25 KGF, 250N forcegauge to measure insertion force though the rubber membrane held in aCole-Parmer 06525-03 Test Fixture/Desiccator by McMaster p/n 5033A5C-clamps.

The following table describes the equipment used in the testing:

TABLE 1 Type of Model or ID No./Serial Equipment Description NumberM5-50 Force gage Mark-10 Series5/ s/n 3479364 50 lbf, 800OFZ, 25 KGF,250 N Orb fixture GYN Cut test fixture/Desiccator, Cole-Parmer#06525-03C-Clamps Steel C-clamp Mcmaster carr# 5033A5 Rubber Test 1″ diameter,0.125* thickness Fda-comliant Silicone Coupons medical grade rubbermembrane. Rubber, plain back 1/8″ thick, 40a Durometer. Angled Test RodsAngled stainless steel rods with Custom machined angled tip, 5 each ofstainless steel angled (20°, 30°, 35°, 45°, 60°, 90°) al rods. 304stainless 5.0 mm OD, and 5 each of steel, medical grade. (20°, 30°, 35°,45°, 60°, 90°) al 5.6 and 5.0 mm OD.

In particular, each of the test rods was inserted through the rubbertest membrane while measuring the insertion forces. For each rod, thetest was performed multiple times. The following tables provide exampleresults:

TABLE 2 Run# Rod Tip Angle Rod# 1 2 3 4 5 20° 1 5.64 5.58 6.59 6.06 6.932 7.33 5.37 6.69 5.64 6.44 3 5.99 5.87 6.28 5.07 7.60 4 5.62 5.41 7.96.94 7.34 5 5.53 5.83 5.18 5.82 5.97 Average 6.02 5.61 6.53 5.91 6.86Overall 6.1848 STD 0.664364 Average

TABLE 3 Run# Rod Tip Angle Rod# 1 2 3 4 5 30° 1 6.48 6.56 6.63 7.1  6.362 6.73 6.63 6.48 5.92 6.18 3 5.87 6.37 6.65 7.34 7.14 4 6.29 6.39 7.497.28 7.18 5 7.26 6.89 6.92 7.13 6.13 Average 6.53 6.57 6.83 6.95 6.60Overall 6.696 STD 0.317807 Average

TABLE 4 Run# Rod Tip Angle Rod# 1 2 3 4 5 35° 1 8.52 8.03 9.37 7.07 8.332 8.53 7.95 7.96 8.45 7.82 3 9.3 8.85 8.95 7.8  8.37 4 7.48 8.67 8.166.79 8.12 5 8.21 8.54 8.99 8.09 8.02 Average 8.41 8.41 8.69 7.64 8.13Overall 8.848 STD 0.599056 Average

TABLE 5 Run# Rod Tip Angle Rod# 1 2 3 4 5 45° 1 8.43 8.91 9.24 9.2110.21 2 8.57 8.53 9.04 8.11 9.46 3 9.3 8.85 8.95 7.8  8.37 4 7.48 8.678.16 6.79 8.12 5 8.77 9.9 8.99 8.09 8.02 Average 8.51 8.97 8.88 8.008.84 Overall 8.6388 STD 0.605667 Average

TABLE 6 Run# Rod Tip Angle Rod# 1 2 3 4 5 60° 1 10.53 9.98 10.43 9.879.72 2 10.13 10.63 9.89 9.73 10.45 3 10.53 9.72 7.46 8.91 9.65 4 10.6210.17 8.93 7.92 9.26 5 9.83 10.23 10.52 9.92 9.82 Average 10.33 10.159.45 9.27 9.78 Overall 9.794 STD 0.346064 Average

FIG. 11 is a plot that graphically shows the test results. Inparticular, FIG. 5 shows an inflection point at just over 30 angulardegrees, where the insertion force as a function of diameter increasesat a greater rate. Thus, for the further testing an angle of 32 angulardegrees for the angle feature was selected.

The testing also tested insertion forces of endoscopes with and withoutsheaths. In particular, an endoscope with the oblique portions discussedabove was tested with and without sheaths, and an endoscope with a bluntfront (90° angle of the distal end to long central axis) was tested. Thefollowing table provides the results:

TABLE 7 Force (lbf) Run#1 Run#2 Run#3 Run#4 Run#5 Real scope prototypeNo Sheath scope 1 4.73 5.25 5.61 5.72 5.16 scope 2 5.73 5.28 4.83 5.395.08 scope 3 5.56 4.92 5.72 4.87 4.28 avg 5.21 STD 0.428517 With sheathscope 1 5.88 6.55 6.58 6.05 6.73 scope 2 5.92 6.13 6.32 6.14 6.23 scope3 5.56 5.96 6.52 5.75 5.65 avg 6.13 STD 0.356448 Normal 5.0 scope(Production) No Sheath 7.43 7.51 6.78 6.76 7.43 avg 7.18 STD 0.377584With Sheath 8.88 8.84 7.64 8.81 8.57 avg 8.55 STD 0.521795 % Diff NoSheath 27.5 % Diff with Sheath 28.3

As shown in Table 7, use of the oblique tip resulted in a 27.5%reduction in insertion force for endoscopes with no sheath, and a 28.3%reduction in insertion force for endoscopes including a sheath, comparedto current endoscopes with blunt fronts (90° angle of the distal end tolong central axis).

Exemplary embodiments are disclosed and variations, combinations, and/ormodifications of the embodiment(s) and/or features of the embodiment(s)made by a person having ordinary skill in the art are within the scopeof the disclosure. Alternative embodiments that result from combining,integrating, and/or omitting features of the embodiment(s) are alsowithin the scope of the disclosure. Where numerical ranges orlimitations are expressly stated, such express ranges or limitationsshould be understood to include iterative ranges or limitations of likemagnitude falling within the expressly stated ranges or limitations(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numericalrange with a lower limit, R_(l), and an upper limit, R_(u), isdisclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R_(l)+k*(R_(u)−R_(l)), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed. Use of broader terms such as “comprises,”“includes,” and “having” should be understood to provide support fornarrower terms such as “consisting of,” “consisting essentially of,” and“comprised substantially of.” Accordingly, the scope of protection isnot limited by the description set out above but is defined by theclaims that follow, that scope including all equivalents of the subjectmatter of the claims. Each and every claim is incorporated into thespecification as further disclosure, and the claims are exemplaryembodiment(s) of the present invention.

While exemplary embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the scope or teachings herein. The embodimentsdescribed herein are exemplary only and are not limiting. Manyvariations and modifications of the compositions, systems, apparatus,and processes described herein are possible and are within the scope ofthe invention. For example, while the first channel of the endoscope isdescribed as being created within the inner tube telescoped within theouter tube, and with the second channel defined between the inner tubeand the outer tube, in other embodiments the second channel may becreated within the inner tube telescoped within the outer tube and withthe second channel defined between the inner tube and the outer tube.Accordingly, the scope of protection is not limited to the exemplaryembodiments described herein, but is only limited by the claims thatfollow, the scope of which shall include all equivalents of the subjectmatter of the claims. Unless expressly stated otherwise, the steps in amethod claim may be performed in any order and with any suitablecombination of materials and processing conditions.

1. (canceled)
 2. A method of assembling an endoscope, comprising:obtaining an outer tube defining a first central axis, a first proximalend, and a first distal tip, and including a first portion at the firstdistal tip defining a first plane that forms an angle of between andincluding 20 and 40 degrees to the first central axis, and a secondportion at the first distal tip defining a second plane perpendicular tothe first central axis; obtaining an inner tube defining a secondcentral axis, a second proximal end, and a second distal tip, andincluding a first portion at the second distal tip defining a thirdplane that forms an angle of between and including 20 and 40 degrees tothe second central axis and a second portion at the second distal tipdefining a fourth plane perpendicular to the second central axis;inserting the inner tube into the outer tube until the first and thirdplanes are coplanar and two channels are defined within the outer tube,the first channel defined within the inner tube and the second channeldefined between the inner tube and an inner surface of the outer tube;inserting a visualization conduit into the second channel; and opticallyexposing the visualization conduit at the first distal end to define aviewing angle parallel to the first central axis.
 3. The method of claim2, wherein the first plane forms an angle between and including 30 and34 degrees.
 4. The method of claim 3, wherein the first plane forms anangle of about 32 degrees.
 5. The method of claim 2, further comprising:attaching the inner tube to the outer tube at the first distal andsecond distal tips; and attaching the inner tube to the outer tube atthe first and second proximal ends.
 6. The method of claim 5, wherein atleast one of the attaching steps includes soldering.
 7. The method ofclaim 2, further comprising: inserting a light fiber bundle into thesecond channel with the visualization conduit; and optically exposingthe light fiber bundle at the second plane.
 8. The method of claim 2,wherein the outer tube further includes: a first dimension measuredperpendicularly to the first central axis and a second dimensionmeasured perpendicularly to the first central axis and at a right angleto the first dimension, the second dimension equal to or smaller thanthe first dimension; a first transition area on a first side of thefirst distal tip between the first portion and the second portion of theouter tube, the first transition area varying between the first portionand the second portion of the outer tube; and a second transition areaon a second side of the first distal tip opposite the first side, thesecond transition area varying between the first portion and the secondportion of the outer tube.
 9. The method of claim 8, wherein, withrespect to the outer tube: the first transition area defines a radius ofcurvature between and including 8% and 20% of the first dimension; andthe second transition area defines a radius of curvature between andincluding 8% and 20% of the first dimension.
 10. The method of claim 2,wherein the inner tube further includes: a third dimension measuredperpendicularly to the second central axis, and a fourth dimensionmeasured perpendicularly to the second central axis and at a right angleto the third dimension, the fourth dimension equal to or smaller thanthe third dimension; a third transition area on a third side of thesecond distal tip between the first portion and the second portion ofthe inner tube, the third transition area varying between the firstportion and the second portion of the inner tube; and a fourthtransition area on a second side of the second distal tip opposite thefirst side, the second transition area varying between the first portionand the second portion of the inner tube.
 11. the method according toclaim 10, wherein, with respect to the inner tube: the third transitionarea defines a radius of curvature between and including 8% and 20% ofthe third dimension; and the fourth transition area defines a radius ofcurvature between and including 8% and 20% of the fourth dimension. 12.The method of claim 2, wherein the outer tube further includes: a firstdimension measured perpendicularly to the first central axis and asecond dimension measured perpendicularly to the first central axis andat a right angle to the first dimension, the second dimension equal toor smaller than the first dimension; a first transition area on a firstside of the first distal tip between the first portion and the secondportion of the outer tube, the first transition area varying between thefirst portion and the second portion of the outer tube; and a secondtransition area on a second side of the first distal tip opposite thefirst side, the second transition area varying between the first portionand the second portion of the outer tube, and wherein the inner tubefurther includes: a third dimension measured perpendicularly to thesecond central axis, and a fourth dimension measured perpendicularly tothe second central axis and at a right angle to the third dimension, thefourth dimension equal to or smaller than the third dimension; a thirdtransition area on a third side of the second distal tip between thefirst portion and the second portion of the inner tube, the thirdtransition area varying between the first portion and the second portionof the inner tube; and a fourth transition area on a second side of thesecond distal tip opposite the first side, the second transition areavarying between the first portion and the second portion of the innertube.
 13. The method of claim 12, wherein, with respect to the outertube: the first transition area defines a radius of curvature betweenand including 8% and 20% of the first dimension; and the secondtransition area defines a radius of curvature between and including 8%and 20% of the first dimension; and wherein, with respect to the innertube: the third transition area defines a radius of curvature betweenand including 8% and 20% of the third dimension; and the fourthtransition area defines a radius of curvature between and including 8%and 20% of the fourth dimension.
 14. The method of claim 13, wherein theinner tube further includes: a cross-sectional shape perpendicular tothe second central axis, the cross-sectional shape defines a straightportion and a curved portion coupled on each end to the straightportion; and a first height measured from an apex of the curved portionto the straight portion, wherein the first height is greater half thefirst dimension of the outer tube, but smaller than an internaldimension of the outer tube measured parallel to the first dimension.15. The method of claim 2, wherein the outer tube is formed from ametallic material.
 16. The method of claim 2, wherein the inner tube isformed from a metallic material.